Modern vehicles include a vast array of sensors, such as air bag sensors, tire pressure sensors, engine sensors, seat belt sensors, and many others. The sensors provide data about the vehicle's operation (e.g., wheel speed, deceleration, etc.) to controller or processor such as an automotive control unit (ACU), an engine control unit (ECU), or other control unit. Based on the sensor communication data received from the sensors on a bus (e.g., a twisted pair or other wired bus), the control unit can determine if an action should be taken (e.g., an airbag deployment, or any vehicle system action).
A peripheral sensor interface 5 (PSI5) protocol and a distributed system interface 3 (DSI3) protocol are example standards defining automotive communication buses. An ECU connected to a communication bus behaves as a voltage supply, for example, and thus, does not necessarily operate as an ohmic voltage source over the bus to the sensors. A network of sensors connected to the ECU through the communication bus can be configured with one or more protection components to prevent device destruction or instabilities. For example, the sensors of the network can have a series of resistors that have a blocking element or feature, which can be inefficient due to certain behavior dependencies. The behavior of the network on the communication bus can be unpredictable due to a relatively low or high ohmic termination on the sensor side of the bus relative to the line impedance, and a low ohmic termination on the ECU side according to ECU specifications providing for it to operate as a low ohmic supply.
Unpredictable signal behaviors of the network can further be problematic as the line or bus length changes from about a half a meter to twelve meters, for example. Different reflection behaviors can occur on the line with an unspecified termination. A typical terminated bus such as a controller area network (CAN) bus utilizes two wires as well, but does not provide the ability to supply the connected bus participants. The CAN communication wires are terminated and used for the data communication. Another two wires would also be required if the bus nodes do not have their own power supply, as is the case for sensors. These two wires can not be terminated, since they have to be driven low ohmic to supply the connected electronic components. The four wires originate from one section or end of the bus, and thus, connecting every sensor with all four of the extended CAN wires is expensive and increases the probability of problems with the more complex connectors.
Another problem is that data rates for some automotive applications (e.g., electrified or hybrid motor drives, or the control of an electronic operated automated transmission gear box), the transmission requires higher data rates than those transmitted over the standard PSI5 or other bus protocols being implemented. The reason for this is that the exchange of messages at low data rate of established sensor busses introduces latency time into the control loop which is extremely critical for the stability of the feedback loop. These problems call for an improved bus system that allows for transmitting data rates in a range that is similar to a CAN bus, but uses two wires to communicate and simultaneously supply the sensors with energy that is delivered from the ECU side.